CMP polishing heads retaining ring groove design for microscratch reduction

ABSTRACT

A chemical-mechanical polish (CMP) machine and fabrication process using the same. The CMP machine has a CMP retaining ring comprising: an inner peripheral surface; an outer peripheral surface; a lower surface adapted to contact and depress an upper surface of a polishing pad during chemical mechanical polishing of a lower surface of a substrate. The substrate is contained within the inner peripheral surface of the retaining ring during chemical mechanical polishing. At least a groove on the lower surface of the retaining ring. At least a portion of the groove has a rounded contour. In an aspect, the groove has a semicircle profile. In another aspect, the groove has a semicircle profile and a curved top corner profile at adjacent to the lower surface of the retaining ring. The retaining ring with a curved portion of groove reduces the accumulation of dried slurry in the groove and thus reduces micro-scratches.

BACKGROUND OF INVENTION

1) Field of the Invention

Embodiments of this invention relate to Chemical Mechanical Polishing(CMP) methods and machines, and particularly to retaining ring designsfor CMP heads and more particularly to retaining ring designs withcurved grooves for reducing microscatches on semiconductor structures.

2) Description of the Related Art

In semiconductor fabrications, the chemical-mechanical polish (CMP)technique is widely used for the global planarization of semiconductorwafers that are used for the fabrication of VLSI (very large-scaleintegration) and ULSI (ultra large-scale integration) integratedcircuits.

FIGS. 1A and 1B are schematic diagrams showing a conventional CMPmachine. The CMP machine comprises a polishing table 10 on which apolishing pad 12 is layered, a polishing head 14 for holding asemiconductor wafer 16 in position, and a nozzle 18 for applying a massof slurry to the semiconductor wafer 16 during the CMP process.

FIG. 1C shows a respective view of the structure inside of the polishinghead 14. As shown, the polishing head 14 includes an air-pressure means20 which applies air pressure to a wafer loader 22 used to hold thewafer 16. In addition, a retainer ring 24 is mounted around the loader22 and the wafer 16, which can retain the wafer 16 in fixed positionduring the CMP process. Moreover, a cushion pad (not shown) is placedbetween the wafer 16 and the loader 22.

A problem of current chemical-mechanical polish (CMP) machines andprocess is the micro-scratches formed on the substrate during the CMPprocess.

The importance of overcoming the various deficiencies noted above isevidenced by the extensive technological development directed to thesubject, as documented by the relevant patent and technical literature.The closest and apparently more relevant technical developments in thepatent literature can be gleaned by considering U.S. Pat. No. 6,386,962(Gotkis et al.) that shows a wafer carrier with retainer ring for achemical-mechanical polish (CMP) apparatus.

U.S. Pat. No. 6,527,624 B1 (Tollers et al.) shows a retaining ring.

U.S. Pat. No. 6,110,025 (Williams et al.) teaches a retainer ring withpassages.

U.S. Pat. No. 6,293,850 B1 (Lin et al.) shows retaining ring with slurrypassages at the bottom of the retainer ring.

U.S. Pat. No. 6,224,472 B1 (Lai et al.) teaches a retaining ring withchannels.

However, the retaining rings can be further improved.

SUMMARY OF THE INVENTION

It is an object of example embodiments of the present invention toprovide a retaining ring for use in a chemical-mechanical polish (CMP)machine.

It is an object of example embodiments of the present invention toprovide a CMP method and a retaining ring having channels with roundedcontour or rounded corners or curved surfaces for use in achemical-mechanical polish (CMP) machine.

An example embodiment of the present invention provides a retaining ringwhich is characterized as follows. A CMP retaining ring, comprising:

-   -   an inner peripheral surface;    -   an outer peripheral surface;    -   a lower surface adapted to contact and depress an upper surface        of a polishing pad during chemical mechanical polishing of a        lower surface of a substrate; the substrate is contained within        the inner peripheral surface of the retaining ring during        chemical mechanical polishing; and    -   at least a groove on the lower surface of the retaining ring and        extending from a position at or adjacent the inner peripheral        surface of the retaining ring, to a position at or adjacent the        outer peripheral surface of the retaining ring;    -   at least a portion of the groove has a rounded contour.

In another aspect, the groove has a semicircle profile.

In another aspect, the groove has a semicircle profile and the groovehas a rounded top corner adjacent to the lower surface of the retainingring.

An example embodiment of a process of the invention is described asfollows. A process for chemical-mechanical polish (CMP) a wafercomprising:

-   -   the wafer is disposed within a polishing head with the        deposition layer facing a polishing table; the wafer is retained        within the polishing head by a retainer ring, and    -   at least a portion of the groove has a rounded contour;    -   supplying a slurry to the polish table and/or polish head;    -   rotating the polishing table and spinning the polishing head to        chemically polish the wafer.

Another aspect further includes: forming a deposition layer on thesurface of the wafer and chemical mechanically polishing the depositionlayer.

Another aspect further includes: the groove has a semicircle profile.

Another aspect further includes: the groove has a semicircle profile andthe groove has a rounded corner adjacent to the lower surface of theretaining ring.

The above advantages and features are of representative embodimentsonly, and are not exhaustive and/or exclusive. They are presented onlyto assist in understanding the invention. It should be understood thatthey are not representative of all the inventions defined by the claims,to be considered limitations on the invention as defined by the claims,or limitations on equivalents to the claims. For instance, some of theseadvantages may be mutually contradictory, in that they cannot besimultaneously present in a single embodiment. Similarly, someadvantages are applicable to one aspect of the invention, andinapplicable to others. Furthermore, certain aspects of the claimedinvention have not been discussed herein. However, no inference shouldbe drawn regarding those discussed herein relative to those notdiscussed herein other than for purposes of space and reducingrepetition. Thus, this summary of features and advantages should not beconsidered dispositive in determining equivalence. Additional featuresand advantages of the invention will become apparent in the followingdescription, from the drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of a retaining ring and methods thereofaccording to example embodiments the present invention will be moreclearly understood from the following description taken in conjunctionwith the accompanying drawings in which like reference numeralsdesignate similar or corresponding elements, regions and portions and inwhich:

FIG. 1A is a schematic top view of a chemical-mechanical polish (CMP)machine for performing a CMP process on a semiconductor wafer accordingto the prior art.

FIG. 1B is a schematic section view of the chemical-mechanical polish(CMP) machine of FIG. 1A according to the prior art.

FIG. 1C is a cross sectional view showing an inside structure of thepolishing head used on the CMP machine of FIGS. 1A and 1B according tothe prior art.

FIG. 2A is perspective view of a retaining ring having rectangulargrooves 204.

FIG. 2B is a close up perspective view a groove in a retaining ringhaving rectangular grooves 204 as shown in FIG. 2A.

FIG. 2C is a cross sectional view of a groove that has slurry particlesthat cause the problems as discovered by the inventors.

FIG. 3A is perspective view of a retaining ring that has non-rectangulargrooves 304 according to an aspect of the invention.

FIG. 3B is a close up perspective view of an embodiment where the groovehas a semicircle profile according to an aspect of the invention.

FIG. 3C is a cross sectional view of a groove that has a semicircleprofile according to an aspect of the invention.

FIG. 3D is a cross sectional view of a groove that has rounded or curvedor non-angular bottom corners and curved sidewalls 316 according to anaspect of the invention.

FIG. 3E is a cross sectional view of a groove that has rounded or curvedor non-angular bottom corners 311, rounded top corners 320 and slantedor sloped sidewalls 322 according to an aspect of the invention.

FIG. 3F is a cross sectional view of a groove 304F that has rounded orcurved or non-angular bottom corners and about vertical sidewalls 316and a flat bottom 316 according to an aspect of the invention.

FIG. 4A is perspective view of a retaining ring that has non-rectangulargrooves 404 and curved top corners according to an aspect of theinvention.

FIG. 4B is a close up perspective view of an embodiment where the groovehas curved top corners according to an aspect of the invention.

FIG. 4C is a cross sectional view of a groove that has a semicircleprofile and curved top corners according to an aspect of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Introduction

Referring now to the drawings and more particularly to FIGS. 2A, 2B, and2C, there is shown a retaining ring 200 over which the aspects of thepresent invention are an improvement. It is to be understood in thisregard that no portion of FIGS. 2A, 2B and 2C is admitted to be priorart as to the present invention. Rather, this these diagrams are aneffort to provide an improved understanding of some of the problems thatare overcome by the aspects of the invention.

FIG. 2A is perspective view of a retaining ring 200 having rectangularshaped grooves 204. The ring has a lower surface 201 (polishing surfaceor pad side surface) that in operation faces the polish pad.

FIG. 2B is a close up perspective view a groove 204 that has non-curvedcorners or edges in the a retaining ring 200.

FIG. 2C is a cross sectional view of a groove 204 that has slurryparticles or other debris 208 that cause the problems as discovered bythe inventors.

Microscratches are a defect caused by the CMP process. Big particlesand/or dry slurry are causes of the microscrathes. Big particle size canbe control by filtration in the supplier's factory and the dried slurryis hard material normally found the in-house slurry delivery relatedcomponents. The forming of dried slurry can occur when the watervaporizes from the slurry droplet spilled on the surface of somepolishing machine components.

The inventors have found that the retaining ring in thechemical-mechanical polish (CMP) machine is a source of dried slurry. Asshown in FIG. 2C, the corner of the groove of the wafer polishing head'sretaining ring was found to accumulate a few chunks of dried slurry. Apurpose of these grooves is to allow the slurry flow in to the waferpolishing head for efficient planarization process. Unfortunately, thedesign of the current retaining ring grooves can cause slurry particlesto accumulate and increase micro scratches.

Example Embodiments of the Grooves of the Invention

Example embodiments of the grooves of the invention have at least aportion of the groove or the surface adjacent to the groove is curved.Examples of curvilinear portions of groove are: semicircle shapedgrooves, arc shapes grooves, groves with rounded bottom corners, grooveswith rounded top corners, grooves with curved sidewalls, grooves withslanted sidewalls, and combinations thereof. The example embodiment ofthe grooves reduce the buildup of dried slurry in grooves and thusreduce microscratches.

As shown in FIG. 3A, a chemical-mechanical polish (CMP) retaining ring300 comprises: an inner peripheral surface 303; an outer peripheralsurface 302; and a lower surface 301. The lower surface 301 is adaptedto contact and depress an upper surface of a polishing pad duringchemical mechanical polishing of a lower surface of a substratecontained within the inner peripheral surface of the retaining ringduring chemical mechanical polishing.

The retaining ring can be economically and speedily fabricated throughthe injection molding, casting or other molding processes. The mold canbe built to contain the sizable cavity with the retaining ring's netshape. The most commonly used materials for retaining ring, normally butnot limited to thermosetting or thermoplastic polymer, is heated tohighly plastic state and forced to flow into the cavity. The solidifiedmolded part or the retaining ring is removed from the cavity and sentfor other finishing or shaping processes.

The retaining ring 300 has grooves 304 on the lower surface 301. Thegrooves 304 preferably extend from a position at or adjacent the innerperipheral surface of the retaining ring, to a position at or adjacentthe outer peripheral surface of the retaining ring. The cross sectionalarea of the groove can be constant or changes along the length of thegroove. Preferably, at least a portion of the groove 304 has a roundedcontour. Preferably the cross sectional shape of the groove is roundedor has rounded corners. Preferably the cross section of the groove doesnot contain a portion (possibly other than the top corner) where twoflat areas meet at a angle, such as a 90 degree angle. Preferably, thegroove has a shape that reduces the amount of dried slurry and otherparticles that accumulates in the groove during a polish operation.

The term “rounded” can mean: curved, or with curved parts: havingcurved, not straight or angular, surfaces or edges.

The grooves may not have the same cross sectional area along the lengthof the groove. The grooves can preferably have a depth between 2 and 15mm. From a top down view, the groove can have any shape, such as astraight shape as shown in FIG. 3A or can be curved or some combinationthereof.

FIG. 3B shows a closer view of a preferred embodiment of the inventionwhere the groove 304C has an about semicircle profile.

FIG. 3C shows a cross sectional view of a groove 304C that has asemicircle cross-sectional profile 310 with a radius 311. The grooves304C have a semicircle profile preferably with a radius 311 between 2 mmand 15 mm. The semicircle profile of the groove helps prevent the slurryparticles from accumulating in the groove.

In the aspect shown in FIG. 3D, the groove 304D has curved sidewalls 316and a rounded bottom corner 312 and a flat bottom 314. The grooves canhave at least one rounded corner. The grooves have rounded corners/edges312 adjacent to the bottom 314 of the grooves. The rounded corners,edges or surfaces 312 can prevent slurry form accumulating in thegroove.

In an aspect, the retaining ring has grooves with rounded top edgesadjacent to the lower surface 301 of the retaining ring.

Referring to FIG. 3E, an aspect is shown where the groove 304E has arounded top corner 320 near the lower surface of the ring. The groovehas a sloped sidewall 322. The groove has a slanted contour. Slantedmeans the sidewall has a least a section that is not at about a 90degree angle with the lower surface 301 of the ring. The groove has arounded bottom corner 311 and a flat 316 bottom. The bottom can be flator curved.

In an aspect shown in FIG. 3F, the CMP retaining ring has a groove haswith about vertical sidewalls 330 and an about horizontal flat bottom316 and at least one rounded corner 311 between the vertical sidewalls330 and the horizontal bottom 316. The grooves can have a width between1 and 30 mm.

FIG. 4A shows another embodiment where the groove 404 has top corner oredge with a curved shape.

FIG. 4B shows a perspective view of the groove 404 with the rounded topcorner 420. In the aspect shown in FIGS. 4B and 4C the groove has asemicircle profile 410 and top rounded corners 420.

FIG. 4C shows a preferred embodiment of the invention of a groove 404Cwith rounded top corners 420 and a semicircle profile 410. In an option,the rounded top corners 420 can have the shape of a arc of a circlehaving a radius 413. In an option, the semicircle profile 410 can haveradius 411.

The retaining ring can have other channels on the lower surface. Also,the lower surface of the retaining ring can further comprise a pluralityof protrusions and recesses or a mixture of both. In addition, theretaining ring can have other passages thru the ring such as a passageconnecting the grooves to the top side of the ring. See e.g., U.S. Pat.No. 6,527,624 B1.

It will be understood that CMP retaining rings embodiments of theinvention may be advantageously used with any type of CMP polishingsystem, pad material and/or polishing slurry, such as where the lower(or pad-side) surface of the retaining ring contacts the polishing padduring polishing. Examples of suitable CMP slurries include, but are notlimited to, Cabot “SS25”, Cabot “SS12”.

It should be noted that the retaining ring and wafer carriers of thepresent invention may be used with any suitable CMP systems such aslinear CMP apparatus or rotary CMP apparatus.

Process Using the Retaining Ring of Aspects of the Invention

The retaining rings of the aspects of the invention can be used in aprocess to CMP a substrate. The substrate is preferably a wafer withlayers formed or deposited thereover. The layers can be insulatingand/or conducting layers. The insulating layers can be comprised ofoxide, (e.g., oxide made from tetraethylorthosilicate (TEOS)) or low-kmaterials. The conductive layers can be metal layers such as copperalloys, or Aluminum alloys.

A process for chemical-mechanical polishing a wafer comprises thefollowing.

The wafer is disposed within a polishing head with the deposition layerfacing a polishing table. The wafer is retained within the polishinghead by a retainer ring.

The retaining ring is a ring according to an aspect of the inventiondescribe above. For example, at least a portion of the groove has arounded contour.

We supply a slurry to the polishing table or the polish head.

We move the polishing table and/or the polishing head to chemicallypolish the wafer. Preferably, we rotate the polishing table and spin thepolishing head to chemically polish the wafer. Preferably the polishtable has a polish pad thereover and the polish pad polishes thesubstrate.

In the above description numerous specific details are set forth inorder to provide a more thorough understanding of the present invention.It will be obvious, however, to one skilled in the art that the presentinvention may be practiced without these details. In other instances,well known process have not been described in detail in order to notunnecessarily obscure the present invention.

Given the variety of embodiments of the present invention justdescribed, the above description and illustrations show not be taken aslimiting the scope of the present invention defined by the claims.

While the invention has been particularly shown and described withreference to the preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade without departing from the spirit and scope of the invention. It isintended to cover various modifications and similar arrangements andprocedures, and the scope of the appended claims therefore should beaccorded the broadest interpretation so as to encompass all suchmodifications and similar arrangements and procedures.

1. A CMP retaining ring, comprising: an inner peripheral surface; anouter peripheral surface; a lower surface adapted to contact and depressan upper surface of a polishing pad during chemical mechanical polishingof a lower surface of a substrate; at least a groove on said lowersurface of said retaining ring; and said groove extending from aposition at or adjacent said inner peripheral surface of said retainingring, to a position at or adjacent said outer peripheral surface of saidretaining ring; at least a portion of said groove has a rounded contouror slanted contour.
 2. The CMP retaining ring of claim 1 wherein saidgroove has a semicircle profile.
 3. The CMP retaining ring of claim 1wherein said groove has a semicircle profile and said groove has arounded top corner adjacent to the lower surface of the retaining ring.4. The CMP retaining ring of claim 1 wherein said groove has asemicircle profile with a radius between 2 and 15 mm.
 5. The CMPretaining ring of claim 1 wherein said groove has at least one roundedcorner.
 6. The CMP retaining ring of claim 1 wherein said groove hasrounded corners adjacent to the bottom of said grooves.
 7. The CMPretaining ring of claim 1 wherein said groove has rounded top cornersadjacent to the lower surface of said retaining ring.
 8. The CMPretaining ring of claim 1 wherein the cross-sectional area of saidgroove changes along the length of said groove.
 9. The CMP retainingring of claim 1 wherein said groove has a width between 1 mm and 30 mm;said groove has a depth between 1 and 15 mm.
 10. The CMP retaining ringof claim 1 wherein said groove has vertical sidewalls or slopedsidewalls.
 11. The CMP retaining ring of claim 1 wherein said groove hasvertical sidewalls and an about horizontal bottom and at least onerounded corner between said vertical sidewalls and said horizontalbottom.
 12. The CMP retaining ring of claim 1 wherein said groove hasstraight sidewalls and top and bottom corners; at least one of saidcorners is rounded or curvilinear.
 13. The CMP retaining ring of claim 1wherein said retaining ring can further comprise other channels; thelower surface of the retaining ring can further comprise a plurality ofprotrusions and recesses or a mixture of both.
 14. A process forchemical-mechanical polishing a substrate comprising: said substrate isdisposed within a polishing head facing a polishing table; saidsubstrate is retained within the polishing head by a retainer ring, andat least a portion of said groove has a rounded contour; supplying aslurry to said polishing table or to said polish head; moving thepolishing table and/or the polishing head to chemically polish thewafer.
 15. The process of claim 14 which further includes: saidsubstrate is a wafer; forming a deposition layer on the surface of saidwafer and chemical mechanically polishing said deposition layer.
 16. Theprocess of claim 14 wherein said groove has a semicircle profile. 17.The process of claim 14 wherein said groove has a semicircle profile andsaid groove has a rounded corner adjacent to the lower surface of theretaining ring.
 18. The process of claim 14 wherein said groove has atleast one rounded corner.
 19. The process of claim 14 wherein saidgrooves has at least one rounded bottom corner.
 20. The process of claim14 wherein said groove has rounded edges adjacent to the bottom of saidgrooves.
 21. The process of claim 14 wherein said groove has rounded topedges adjacent to the lower surface of said retaining ring.
 22. Theprocess of claim 14 wherein said groove has a width between 1 and 30 mm;said groove has a depth between 1 and 15 mm.